Mathematical Modeling And Parameter Estimation Of Mfi Membranes For Para/Ortho-Xylene Separation

A mathematical model of a membrane with a thin, oriented, and selective MFI layer, which also includes contributions from defects, pore blockages, support layer, and external mass transfer, was formulated based on the Maxwell-Stefan equations. It was validated using reported (Kim et al., Angew Chemie Int Ed, 2018, 57:480-485; Jeon et al., Nature, 2017, 543:690-694) para/ortho-xylene separation data from five MFI membranes. The diffusivities of the xylenes were considered to be the same for all membranes, while the thickness and the density of defects and pore blockage were treated as unique properties of each membrane, and their contributions were estimated by fitting the model to the corresponding separation data. The effects of these properties and the role of permeate pressure on the separation performance were subsequently analyzed. The proposed modeling, parameter estimation, and analysis framework allow one to quantitatively interpret the variation of separation performance, to understand separation bottlenecks, and to provide guidance for designing membranes with desired performance.